Electronically controlled continuous lubricating oil replacement system

ABSTRACT

An improved method and system for automatically continuously replacing an engine&#39;s used lubricating oil with fresh lubricating oil throughout operation based on engine operating conditions is disclosed. The present system includes an injection control device for injecting small amounts of used lube oil into the engine&#39;s fuel system and an auxiliary flow control device for directing controlled quantities of fresh oil into the engine&#39;s lube oil system. An electronic controller is provided to vary the amount of used lube oil injected into the oil system based on the severity of engine operation. The process periodically determines an engine operating severity value, i.e. fuel consumption value, for an interval of engine operation and calculates a base line quantity of oil for injection based on the current fuel consumption of the engine during the current interval. The system also includes a diagnostic process for maintaining the engine&#39;s oil sump at a proper level while monitoring various components and parameters of the system and providing an indication of any abnormal condition. The system maintains the quality of the engine lube oil at a level necessary to provide optimal engine protection at all engine operating conditions while also maintaining the oil concentration in the engine&#39;s fuel at an acceptable level.

This is a Continuation application Ser. No. 09/007,048, filed Jan. 14,1998, now U.S. Pat. No. 5,881,688 which is a Continuation applicationSer. No. 08/608,305, filed Feb. 28, 1996, now U.S. Pat. No. 5,749,339.

TECHNICAL FIELD

This invention relates to an improved system for automatically,continuously replacing an engine's used lubricating oil with freshlubricating oil throughout engine operation based on engine operatingconditions.

BACKGROUND OF THE INVENTION

It is highly desirable to be able to minimize the amount of servicerequired for internal combustion engines to thereby minimize theinterruption in the use of the vehicle/equipment. Degradation andcontamination of engine lubricating oil during engine use requires oilchanging procedures which account for a significant portion of themaintenance and associated engine "down time". Conventional periodic oilchanges generate an accumulation of waste lubricating oil which must bedisposed of and/or processed resulting in undesirable costs. Therefore,extending oil drain intervals and reducing waste disposal are of greatvalue to vehicle/equipment operators.

Consequently, systems have been developed for automatically changinginternal combustion engine crankcase oil during engine operation. Forexample, U.S. Pat. No. 3,447,636 discloses a system for automaticallychanging engine oil while the engine is operating. The system operatesto drain substantially all of the used oil from the engine immediatelyprior to introducing fresh oil into the engine from a reservoir. Thesingle operation process results in a complete change of thesubstantially the entire engine oil volume. However, draining the engineprior to refilling with fresh oil necessarily creates a risk that aninadequate supply of lube oil exists in the engine for an interim timeperiod possibly resulting in damage or excessive wear to enginecomponents from insufficient lubrication. Moreover, this systemundesirably results in a quantity of waste oil.

Other systems have been developed which automatically change engine lubeoil during engine operation while avoiding a waste quantity of oil bydirecting the used lube oil into the fuel system for burning with thefuel in the engine. These systems periodically drain a small amount ofthe used oil from the engine lube oil system, and replace the drainedquantity with fresh lubricant from an auxiliary tank. For example, U.S.Pat. Nos. 4,869,346 and 5,390,762 to Nelson disclose an automaticcrankcase oil change and makeup system including a displacement unithaving a piston with a predetermined stroke set to deliver identical,predetermined amounts of fresh oil during each stroke at the same flowrate and volume as the extraction of used oil. The frequency of thepressure strokes is set by a timer in an electronic controller, and isadjustably set to stroke at fixed time intervals to provide a cumulativequantity of fresh oil to the crankcase according to the regularrecommended oil change period for the particular engine. A pair of dialson the controller enable the frequency of the pressure strokes to beadjusted. U.S. Pat. Nos. 4,421,078; 4,495,909; and 5,431,138 to Hurnerdisclose similar systems for oil changing and making up during engineoperation which include a control module having an adjustable impulsetimer set to periodically cycle an air pressure operated oil extractorpump at a fixed time intervals to direct a predetermined amount ofengine oil out of the oil pan and into the fuel tank. Fresh makeup oilis pumped from an oil reservoir to the crankcase, also by air pressure,in response to a low level signal from a dipstick sensor. Similarly,U.S. Pat. No. 4,417,561 to Yasuhara discloses an automatic oil changingand disposing apparatus wherein used crankcase oil is periodicallydirected to a fuel tank via a valve controlled by an odometer switch,and fresh oil is gravity fed from a fresh oil tank to the crankcase viaa control valve controlled by a crankcase oil level switch. The quantityof each increment of used oil removed from the crankcase, and eachincrement of fresh oil supplied, is controlled by respective timershaving variable on-time duration to effect variable control of engineoil extraction and addition.

Although capable of automatically changing lube oil during engineoperation, the automatic oil changing systems discussed hereinabove areincapable of accurately varying and controlling oil changing in responseto the actual needs of the engine that vary based on the engineoperating conditions, such as fuel consumption. The amount of oildrained from the crankcase and injected into the fuel system is ofteneither less than the necessary replacement rate when the engine is beingused more heavily than expected, or more than the optimum amount whenthe engine is being used less heavily than expected. Injecting toolittle used oil from the oil sump into the fuel system willdisadvantageously result in engine damage from over-used oil incapableof adequately lubricating and cooling engine components. On the otherhand, injecting too much oil results in excessive concentrations of usedoil in the fuel resulting in engine performance degradation, increasedemissions, shortened fuel filter life and wasted oil. In addition, ifthe engine is a recent emission regulated engine, injecting too much oilinto the fuel system will result in emission non-compliance and possiblya fine. Although Yasuhara '561 suggests variable control of engine oilextraction and addition, this reference does not suggest means foraccomplishing such variable control nor the engine operating parametersto be considered. The Nelson '346 and '762 references only suggestvarying the amount of oil extracted and added to the engine crankcase bymanually adjusting timers to vary the frequency of oil additions andextractions.

British application No. 867,711 discloses a system for creating acontrolled injection of engine lubricating oil into the engine's fuelsystem. The amount of oil added to the fuel system may be controlled independence on engine load in a first embodiment or engine speed in asecond embodiment. In both embodiments, oil is injected into the fuelsystem via a groove formed in a fuel injection pump plunger. In thefirst embodiment, the annular groove is shaped with a varyingcross-section. The plunger is rotated based on engine load to vary theflow area of the groove thereby varying the amount of injected oil. Inthe second embodiment, oil injection is controlled based on engine speedby varying the oil pressure in the suction chamber. A fuel passagecontaining a throttle orifice connects the fuel supply pump to thesuction chamber. As the volume of fuel injected increases, the pressurein the suction chamber decreases which draws a larger quantity of oilinto the chamber. However, each embodiment of this system is incapableof controlling oil injection based on more than one engine condition. Asa result, each embodiment of this system is incapable of effectivelyvarying the rate of oil injection to maintain the proper quality of lubeoil in the sump while also ensuring an acceptable concentration of oilin the fuel. In addition, this system does not provide an automaticmeans for replacing the engine's oil sump. Also, since this systemrequires modifications to an engine's fuel pump, this system may not beeasily retrofit on existing engines.

U.S. Pat. No. 4,674,456 to Merritt discloses a system for effectingperiodic partial replacement of used oil with fresh oil. A firstcontainer holds fresh oil, a second container holds used oil, andseparate respective pumps transfer fresh oil to the engine and removeused oil. In operation, fresh oil approximating the total capacity ofthe crankcase or oil reservoir is poured into the first container. Inthe example provided by Merritt, if the manufacturer recommends thatfive quarts of oil be replaced every 3000 miles, the system isprogrammed to remove one quart of used oil after 600 miles. Thecontrolling means senses the engine running time or the miles driven andactivates the respective pumps at each running time or mileage interval.Fresh oil is added at a substantially equal rate to the rate of oilremoval from the crankcase to maintain a constant amount of oil withinthe oil reservoir of the engine. The controlling means may receive amodifying input signal from a thermocouple measuring engine temperatureto increase the rate of oil replacement if above-average enginetemperature is measured. However, varying the amount of predeterminedoil replacement based merely on variations in the engine operatingtemperature does not result in the optimum lube quality throughoutengine operation. Moreover, this system does not provide any means forcompensating for oil burned in, or inadvertently leaked from, theengine. In addition, this system does not direct used oil into theengine' fuel system and, therefore, undesirably results in a quantity ofwaste oil which must be disposed of or processed.

U.S. Pat. No. 4,506,337 to Yasuhara is noted for disclosing an enginelube oil replacement timing monitoring system comprising a microcomputerwhich calculates the amount of soot suspended in the lube oil on thebasis of engine speed and engine load whereby the expired life of theengine oil can be accurately detected so as to permit oil changing. Themicrocomputer operates an indicator alerting the operator of the need tochange the oil. Thus, instead of automatically changing the oil duringengine operation, this system disadvantageously requires the engine tobe shut down prior to changing the oil and inevitably produces aquantity of waste oil which must be disposed of. In addition, thissystem fails to consider other critical engine operating conditions andparameters and, therefore, does not determine the optimum time intervalbetween oil changes nor maintain the quality of the oil at an optimumlevel throughout engine operation.

Therefore, there is a need for a continuous engine lube oil replacementsystem capable of more effectively controlling the quantity of used lubeoil burned in the engine based on varying engine operating conditions.

SUMMARY OF THE INVENTION

It is an object of the present invention, therefore, to overcome thedisadvantages of the prior art and to provide a continuous lube oilreplacement for an engine capable of reliably, accurately andeffectively controlling the rate at which lube oil is replaced in theengine's lube oil system.

It is another object of the present invention to provide a continuousoil replacement system capable of burning only the optimal quantity oflube oil in the engine's fuel system.

It is yet another object of the present invention to provide acontinuous oil replacement system which eliminates oil changes so as tominimize engine down time.

It is a further object of the present invention to provide a continuousoil replacement system which accurately and effectively maintains theoil concentration in the engine's fuel system at a level necessary tomaintain emissions compliance.

It is a still further object of the present invention to provide acontinuous oil replacement system which maintains the quality of theengine lube oil at a level necessary to provide optimal engineprotection.

Still another object of the present invention is to provide anelectronically controlled continuous oil replacement system capable ofoptimally controlling the amount of waste oil directed into the engine'sfuel system based on varying engine operating conditions to achieveoptimum engine lubrication at reduced costs during all engine operatingconditions.

Another object of the present invention is to provide an electronicallycontrolled continuous oil replacement system which continuously monitorsand maintains the engine lube oil sump at the proper level therebyeliminating the costs and risks associated with manual inspections bythe vehicle operator.

Yet another object of the present invention is to provide anelectronically controlled continuous oil replacement system whicheliminates the need to dispose of used engine oil.

Still another object of the present invention is to provide anelectronically controlled continuous oil replacement system which avoidsexcessive engine oil consumption under light engine loads andunacceptable oil contamination under heavy engine loads.

Another object of the present invention is to provide an inexpensiveelectronically controlled continuous oil replacement system which can beeasily retrofit on existing engines and integrated into new engines.

Still another object of the present invention is to provide anelectronically controlled continuous oil replacement system whichautomatically continuously monitors various components and parameters ofthe engine lube oil system and the oil replacement system and provideswarning indications of any abnormal conditions.

It is a further object of the present invention to provide anelectronically controlled continuous oil replacement system whichaccurately and effectively maintains the oil concentration in theengine's fuel system at a level necessary to maintain sulfurconcentration in the fuel at an acceptable level.

These and other objects are achieved by providing an electronicallycontrolled lube oil replacement system for an engine capable ofconsuming fuel, comprising an engine lube oil supply including a lubeoil supply circuit for delivering a supply of lube oil to the engine, alube oil injection circuit connected to the lube oil supply circuit forpermitting an injection flow of lube oil from the lube oil supplycircuit, an engine lube oil injection control device positioned alongthe lube oil injection circuit for controlling the injection flow oflube oil to define a lube oil injection rate, an engine operatingcondition detecting device for detecting at least one operatingcondition and generating an engine operating condition signal indicativeof the engine operating condition or mode, and a processor for receivingthe engine operating condition signal, calculating a engine operatingseverity value based on the engine condition signal and generating aninjection flow control signal based on the engine operating severityvalue, wherein the injection flow control signal controls the operationof the injection control device to variably control the injection rate.The engine operating severity value may be a fuel consumption valuecorresponding to the engine fuel consumption rate or total quantity fora current interval. The lube oil injection circuit may be connected to afuel supply system for injecting lube oil into the fuel supply systemfor burning. The replacement system may also include an auxiliary lubeoil supply including an auxiliary lube oil supply circuit for providingan auxiliary supply flow of lube oil to the main lube oil supply and anauxiliary lube oil tank containing a supply of auxiliary lube oil. Thepresent replacement system may also include an auxiliary lube oil flowcontrol device positioned along the auxiliary lube oil supply circuitfor controlling the auxiliary supply flow of clean lube oil to theengine lube oil supply to define an auxiliary supply flow rate. Theprocessing means may generate a flow control signal for controlling theoperation of the auxiliary lube oil flow control device so as tovariably control the auxiliary supply flow rate. The engine lube oilsupply may include a lube oil sump containing an accumulated supply oflube oil while the auxiliary lube oil may include an auxiliary lube oiltank. The auxiliary lube oil supply circuit may connect the auxiliarylube oil tank to the lube oil sump for delivering an auxiliary supplyflow to the main sump. A lube oil sump level sensor may also be providedto detect the oil level in the sump and generate a corresponding levelsignal. The processing means may receive the level signal and generatean auxiliary control signal for controlling the operation of theauxiliary supply flow control device to maintain the sump oil level atan acceptable level. The engine lube oil injection control device mayinclude an injection pump intermittingly operated to pump apredetermined quantity of lube oil into the fuel supply system. Theauxiliary flow control device may include a similar injection pump fordirecting predetermined quantities of auxiliary lube oil into the sump.An electronic control module may be provided for controlling engineoperation and providing the engine condition signal to the processingmeans. The engine condition signal may be an integrated fuel consumptionrate with respect to time, or an alternative value. The processor may bean electronic controller including an input for receiving the enginecondition signal and an output for providing the injection flow controlsignal. The processor may calculate a fuel consumption value based onthe engine condition signal, process the fuel consumption value todetermine the quantity of oil to be injected, generate an output signalbased on the quantity oil to be injected and provide the output signalto the output. The electronic controller may further include an engineconfiguration storage device connected with the processor for storingengine configuration information. The processor may process the fuelconsumption by accessing the engine configuration storage device andretrieving an oil change value corresponding to the quantity of oil tobe injected into the fuel system based on the fuel consumption value.

In the method of the present invention, the quantity of oil to beinjected is determined at periodic intervals throughout engine operationbased on a predetermined time variable or a predetermined mileagevariable or combination thereof. The injection control device is capableof injecting a predetermined unit injection quantity upon receipt of theoutput signal so that the timing of injection of the predetermined unitinjection quantity during engine operation is dependent on the fuelconsumption value. The method may also include the step of adding thequantities of oil to be injected for a plurality of periodic intervalsto define a cumulated oil quantity to be injected. The cumulatedquantity of oil to be injected may then be compared to the predeterminedunit injection quantity. The output signal is provided to the injectioncontrol device when the cumulated oil quantity to be injected is greaterthan the predetermined unit injection quantity. The method may alsoinclude the step of detecting oil temperature, generating a temperaturesignal indicative of the oil temperature and adjusting the quantity ofoil to be injected based on the temperature signal. A step may also beincluded for accessing from a soot information storage device toretrieve a soot value. The quantity of oil is then adjusted based on thesoot value. The method may also include the step of adjusting thequantity of oil to be injected based on a quality characteristic of thelube oil.

The present lube oil replacement system also includes a diagnosticsystem and method for determining an engine sump oil level and providinga first control signal to the auxiliary flow control device to inject afirst quantity of auxiliary oil from the auxiliary lube oil tank to theengine sump when the engine sump oil level is below an acceptable level.The diagnostic method may include the step of redetermining the enginesump oil level after injection with the first quantity of auxiliary oildetermining an auxiliary oil level in the auxiliary oil tank when theengine sump level is unacceptable and generating a fault signal foralerting an operator when the auxiliary oil tank level is low. Moreover,this method may include the step of determining whether the auxiliaryflow control device is functioning properly when the engine sump oillevel is higher than an acceptable level and generating a fault signalfor alerting an operator when the auxiliary flow control device isfunctioning improperly. The method may also include the step of checkingthe proper functioning of the flow control device after determining theauxiliary oil level in the auxiliary oil tank.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a schematic diagram of the continuous lube oil replacement systemof the present invention;

FIG. 2 is a schematic block diagram of a controller for use with the oilreplacement system of the present invention;

FIG. 3 is a flowchart illustrating an oil injection process forcalculating the quantity of oil to be injected into the fuel system ofthe internal combustion engine and controlling the timing of theinjection of such oil into the fuel system in accordance with thepresent invention;

FIG. 4 is a flowchart illustrating in more detail the step ofdetermining the oil quantity to be injected as shown in FIG. 3;

FIG. 5 is a flowchart illustrating a second embodiment of the processfor determining the oil quantity to be injected; and

FIG. 6 is a flowchart illustrating a diagnostic process for monitoringthe amount of available oil in a lube sump, for replacing such amountfrom an auxiliary oil tank when necessary and for providing externalindications of the condition of the oil replacement system to anoperator of a vehicle.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the continuous lube oil replacement system of thepresent invention indicated generally at 10 includes an engine lube oilsupply system 12 for supplying lubricating fluid or oil to an engine forlubricating and cooling engine components, a lube oil injection circuit14 for draining small quantities of used lube oil from the engine lubeoil circuit, an injection control or metering device 16 positioned alongthe lube oil injection circuit 14 for controlling the injection rate oflube oil from the engine lube oil supply circuit and a controller 18 fordetermining an optimum injection rate of lube oil in response to engineoperating conditions and controlling injection control device 16 toachieve the optimum injection rate. The continuous lube oil replacementsystem 10 may be used to inject the lube oil into an engine fuel system,indicated generally at 20, for mixing and burning with the fuel in theengine's combustion chamber. Oil replacement system 10 also preferablyincludes an auxiliary lube oil supply system indicated generally at 22for supplying new lube oil to the lube oil supply circuit. The presentoil replacement system 10 advantageously removes predeterminedquantities of used oil from the engine lube oil system 12 throughout theoperation of the engine based on specific engine characteristics andoperating conditions to create an optimum drain or injection rate whilesupplying controlled quantities of new oil to engine lube oil system 12.As a result, the present system maintains the lube oil concentration inthe fuel below a predetermined level necessary to maintain emissionswithin acceptable limits while also maintaining the lube oil in theengine lube oil system 12 at a quality necessary to achieve optimumengine lubrication and cooling throughout extended periods of engineoperation without incurring the down-time and costs associated withcomplete one-time engine lube oil replacement.

The engine lube oil supply system 12 includes an engine lube oilcrankcase or sump 24, a lube oil supply circuit 26 for delivering lubeoil to the engine and a lube oil pump 28 positioned along supply circuit26 for drawing lube oil from sump 24 and providing a pressurized flow oflube oil to the engine. Throughout operation of the engine, lube oil isdelivered to the engine for lubricating and cooling various enginecomponents and then returned to oil sump 24. Without proper lube oilreplacement or replacement, the ability of the oil to lubricate and coolgradually decreases during use due to oil degradation and contamination.The present system provides optimal oil replacement to maintain thequality of the lube oil while also maintaining emissions fuel sulfurcontent within acceptable limits.

The lube oil injection circuit 14 connects at one end to engine lube oilsupply circuit 26 downstream of lube oil pump 28 and at an opposite endto the engine fuel system 20. Engine fuel system 20 may be anyconventional engine fuel system for delivering fuel to the engine. Forexample, as shown in FIG. 1, fuel system 20 includes a fuel tank 30 anda fuel supply circuit 32 connecting fuel tank 30 to the engine. Fuelsystem 20 further includes a fuel pump 34 positioned along fuel supplycircuit 32 and a fuel filter 36 positioned between pump 34 and theengine. A fuel return line 38 returns unused fuel from the engine tofuel tank 30.

Lube oil injection circuit 14 preferably connects to fuel system 20along fuel supply circuit 32 between fuel pump 34 and fuel filter 36.However, alternatively, injection circuit 14 may be connected to fuelreturn line 38, the fuel tank 30 or to fuel supply circuit 32immediately upstream of fuel pump 34, i.e. fuel pump inlet. It has beenfound that directing the lube oil into the fuel pump inlet providesimproved mixing of the fuel and lube oil while also enhancinglubrication of fuel pump 34. Lube oil injection control or meteringdevice 16 is positioned along lube oil injection circuit 14 to controlthe injection of lube oil from sump 24 and injection into fuel supplycircuit 32. Lube oil control device 16 is preferably thesolenoid-operated piston type disclosed in U.S. Pat. Nos. 4,421,078 and4,495,909, which are hereby incorporated by reference, wherein acylinder contains a movable piston defining opposed chambers. Onechamber receives lube oil from the lube oil supply circuit 26 via asolenoid valve while the opposite chamber communicates with apressurized driving fluid via a respective solenoid. The oil deliveredfrom circuit 26 into the chamber is pumped into fuel system 20 as thepiston moves in response to a pressurized driving fluid entering theopposite chamber. The driving fluid may be pressurized air or the lubeoil from the engine lube oil supply system. Each time lube oil controldevice 16 is operated, as dictated by controller 18, the solenoid valvesof control device 16 are actuated to control the flow of lube oil anddriving fluid in a manner to inject a predetermined amount of lube oilfrom one chamber into fuel system 20. The amount of lube oil injectedduring each actuation of injection control device 16 is determined bythe size of the chamber and the fixed stroke of the piston. Preferably,the volume of the chamber, and therefore the volume of lube oilinjected, is relatively small, for example, one ounce. By injectingsmall quantities of lube oil periodically over the operation period ofthe engine, the present system is more capable of precisely controllingthe concentration of lube oil in the fuel so as to maintain emissionswithin acceptable limits throughout engine operation.

Of course, lube oil control device 16 may be any metering or pumpingdevice capable of being selectively operated to inject a precisequantity of lube oil. For example, lube oil control device 16 may be asolenoid operated two-way valve movable between open and closedpositions. A flow restriction orifice is preferably incorporated in thecontrol valve or provided immediately downstream to limit the quantityof lube oil per unit time. The amount of lube oil injected is thereforeis determined primarily by the amount of time the solenoid valve remainsin the open position and secondarily by the lube oil pressure.Therefore, instead of delivering a fixed quantity of lube oil duringeach actuation as does the solenoid operated piston pump previouslydiscussed, the solenoid valve of this embodiment could be actuated andheld in the open position for a period of time necessary to inject anydesired predetermined amount of lube oil. Alternatively, lube oilcontrol device 16 may be of the type disclosed in U.S. Pat. No.5,431,138.

Auxiliary lube oil supply system 22 includes an auxiliary lube oil tank40 containing a reserve or auxiliary supply of lube oil and an auxiliarylube oil supply circuit 42 fluidically connecting tank 40 to lube oilsump 24. The system 22 further includes an auxiliary lube oil supplyflow control or metering device 44 positioned along auxiliary supplycircuit 42 for controlling the flow of auxiliary oil to sump 24. Lubeoil supply control device 44 is preferably the same type of solenoidoperated piston pump as injection control device 16 describedhereinabove. Upon receipt of an actuation signal from controller 18,auxiliary lube oil flow control device 44 operates to inject a fixedquantity of lube oil. Of course, like injection control device 16,auxiliary oil flow control device 44 may alternatively be asolenoid-operated two-way valve capable of injecting variable quantitiesof lube oil as described hereinabove. The lube oil level in sump 24 ismonitored during engine operation via sensors mounted in a sensingchamber 46 mounted external, but fluidically connected to, sump 24. Whenthe oil level in sump 24 reaches a predetermined level below the normaloperating level, controller 18, which receives level signals from thelevel sensors, actuates auxiliary lube oil flow control device 44 toinject auxiliary lube oil so as to maintain a predetermined level insump 24. Alternatively, a float-type device may be used in combinationwith a gravity drain version of the present system. In this embodiment,auxiliary tank 40 must be positioned above sump 24 and a valvepositioned in the auxiliary supply circuit 42 is controlled by thefloat-type device such that the valve is opened when the oil level insump 24 is low and closed when the oil level reaches an acceptablepredetermined level.

Alternatively, the system may be designed to detect sump oil level onlyprior to each engine start-up, when the level can be accuratelydetected, instead of continuously or intermittently throughout engineoperation. In over-the-road vehicles applications, the sump oil levelmay be difficult to accurately detect due to churning of the oil by theengine crankshaft and vehicle movement. By only detecting sump levelduring engine shut-down, an accurate sump level can be detected. If thesump level is below an acceptable level, than the auxiliary flow controldevice can be operated to add the necessary amount of oil to the sump.

In an alternative embodiment, the auxiliary system may include a dualfunction flow control device which in a single operation injects thesame amount of fresh oil into sump 24 and used oil from the sump intothe fuel system. The dual function flow control device may, for example,be similar to that disclosed in U.S. Pat. No. 4,869,346. Thus, when thesystem of the present invention signals the dual function flow controldevice to inject a quantity of used lube oil into the fuel system, theflow control device will operate to remove a unit injection quantityfrom the sump while delivering an identical quantity of fresh oil to thesump. Since the oil level in sump may fall below a predetermined leveldue to oil leakage from the engine or gradual oil burning in the engine,this embodiment may include an automatic used oil recirculation system.If the sump level is substantially below the predetermined level, thenat least a portion of the quantity of used oil to be injected isreturned to the sump until an acceptable level is reached.

FIG. 2 is a block schematic diagram of the control and operatingcircuitry of continuous oil replacement system 10. This circuitry maycomprise the controller 18, injection control device 16, electroniccontrol module 19, auxiliary lube oil flow control device 44, statusindication lamps 202, J1786 bus 204, speed sensor 206, rail pressuresensor 208, auxiliary tank level sensor 210, and sump level sensor 212.

Controller 18 comprises main microcontroller 214, memory 216, datalinkinterface 218, solenoid controller 220, secondary microcontroller 222,SAE J1783 datalink interface 224, digital input 226, frequency input228, analog input 230, and engine type selection switches 232.

As shown in FIG. 2, main microcontroller 214 is connected to memory 216,which is preferably an EEPROM containing a control program, initialsetup data, and operating tables used by main microcontroller 214. Thecontrol program, data, and operating tables implement novel controlalgorithms which will be described in more detail below with referenceto FIGS. 3-5.

Main microcontroller 214 has input ports connected to receiveinformation from analog input 230, frequency input 228, and digitalinput 226. Main microcontroller 214 also has an input/output portconnected to datalink interface 218 and an output port connected tosolenoid controller 220. Main microcontroller 214 is further connectedvia a data bus to secondary microcontroller 222 which has input portsconnected to digital input 226, output ports connected to signal lamps202, and an input/output port connected to SAE J1783 datalink interface224.

Solenoid controller 220 is connected to selectively actuate solenoids ofinjection control device 16 and auxiliary lube oil flow control device44 under control of the program in main microcontroller 214. Solenoidcontroller 220 is a solenoid control circuit which receives a digitalcontrol signal from main microcontroller 214 and provides a high-currentoutput to actuate the connected solenoids. Injection control device 16,when actuated under the control of main microcontroller 214, diverts oilfrom circuit 26 of the engine's lubricating oil system (shown in FIG. 1)to engine fuel system 20 (also shown in FIG. 1). Auxiliary lube oil flowcontrol device 44, when actuated, transfers lubricating oil fromauxiliary lube tank 40 (shown in FIG. 1) to lube sump 24 (also shown inFIG. 1).

As will be seen, the operating program of main microcontroller 214 usesengine operating condition inputs, such as fuel consumption, or speedand rail pressure inputs, to determine a fuel consumption value and, inreal time, an appropriate rate of lubricating oil burning andreplacement based on current operating conditions. Injection controldevice 16 and auxiliary lube oil flow control device 44 are controlledto provide the desired rates of lubricating oil burning and replacement.

FIG. 2 shows three different sets of connections for obtaining theneeded fuel consumption information, but it will be understood that onlyone source of this information is needed. The inputs may be obtainedfrom dedicated speed sensor 206 and rail pressure sensor 208 shown inFIG. 2. These inputs are preferred in cases where there is no electroniccontrol module 19 or SAE J1786 bus 204 on the engine.

However, a conventional ECM for controlling injection metering for anelectronic fuel injection system possesses the required fuel consumptioninformation, i.e. instantaneous fuel consumption rate. Thus, in engineshaving an ECM 19, the ECM 19 will typically directly provide therequired fuel consumption information. The fuel consumption informationcan be transmitted to main microcontroller 214 through datalinkinterface 218. Datalink interface 218 may be a serial bidirectionaldigital interface compatible with electronic control module 19, and mayreceive sensor or fuel consumption information and report the status ofcontroller 18 and continuous oil replacement system 10 to ECM 19. In thecase where ECM 19 is provided and ECM 19 provides the necessary fuelconsumption information, it is not necessary to provide continuous oilreplacement system 10 with a separate, dedicated speed sensor 206 andrail pressure sensor 208.

As a further alternative, the necessary engine operating information(speed and rail pressure), used to calculate the fuel consumption value,can be obtained by monitoring data transmissions on an SAE J1786 bus 204if the engine is so equipped. In this case, controller 18 can operateusing existing engine sensors and by communicating over SAE J1786 bus204. Datalink interface 224 is a serial bidirectional interfacecompatible with the SAE J1786 bus standard. Secondary microcontroller222 receives data packets through datalink interface 224 containing thedesired speed and rail pressure information, and may transmit statusinformation for continuous oil replacement system 10 over bus 204. Speedsensor 206, rail pressure sensor 208, and datalink interface 218 may allbe omitted in this embodiment if the necessary data reception and statusreporting functions can be performed over bus 204.

Engine type selection switches 232 may be DIP switches, jumpers, orother switch devices allowing an installer to configure the controller18 for operation with one of a plurality of engines. The settings ofengine type selection switches 232 are read by main microcontroller 214through digital input 226 during startup, and these settings may then beused to select operating programs, data tables, sensor information inputsources, and methods of information output, depending on theconfiguration of the engine and its electronic systems.

Analog input 230 is an analog-to-digital converter which provides mainmicrocontroller 214 with a digital representation of the output signallevel produced by analog sensors, such as the pressure and level sensorsshown. Sump level sensor 212 and auxiliary tank level sensor 210preferably provide a DC voltage output which varies with the respectiveoil levels monitored by these sensors. Rail pressure sensor similarlyprovides a DC voltage output varying with fuel injection rail pressure.

Frequency input 228 is a frequency counter which provides a digitalrepresentation of the frequency of a pulsed signal, such as the outputof speed sensor 206 which may be, for example, a Hall-effect or opticalsensor attached to a rotating engine shaft to produce a pulsed outputsignal, the frequency of which varies with engine speed.

Secondary microcontroller 222 is a microcontroller comprising RAM andROM memory, input and output ports, and an operating program. Theoperating program receives digital inputs from engine type selectionswitches 232 and a digital control signal from main microcontroller 214.Based on these signals, secondary microcontroller 222 provides an outputsignal to control status indication lamps 202 in a manner which will bedescribed in more detail below. In addition, secondary microcontrollercontrols datalink interface 224, transmitting information received frommain microcontroller 214 over bus 204 and providing engine operatingparameter information received over bus 204 to main microcontroller 214.Thus, secondary microcontroller 222 performs input and output processingfunctions to offload duties from main microcontroller 214.

Having discussed the structure of the continuous oil replacement systemaccording to the present invention, the method used by the system toensure proper engine oil replacement will now be discussed in moredetail. Specifically, the most preferred embodiment of the presentinvention includes two fundamental processes--a first oil injectionprocess for calculating the quantity of oil to be injected into the fuelsystem of the internal combustion engine based on the severity of engineoperation as indicated by, for example, current fuel consumption, andfor controlling the timing of the injection of such oil into the fuelsystem; and a second diagnostic process for monitoring the amount ofavailable oil in lube sump 24, for replacing such amount from auxiliaryoil tank 40 when necessary and for providing external indications of thecondition of the oil replacement system to an operator of a vehicle.

As discussed above, in the most preferred embodiment of the presentinvention, both the oil injection process and the diagnostic processwill be implemented in software contained in an oil replacementelectronic control module, or controller 18, that includes a centralprocessing unit such as a micro-controller, micro-processor, or othersuitable micro-computing unit. The controller 18 receives appropriateinputs from the oil replacement system and from the internal combustionengine, and processes these inputs to determine the timing and quantityof oil injection and the appropriate oil replacement and diagnosticservices.

Referring first to FIG. 3, a flowchart illustrating an oil injectionprocess for calculating the quantity of oil to be injected into the fuelsystem of the internal combustion engine and controlling the timing ofthe injection of such in accordance with the present invention is shown.As can be seen in FIG. 3, the process begins at block 300 when aninternal combustion engine containing an oil replacement system inaccordance with the present invention is started. Upon starting of theinternal combustion engine, the oil replacement controller 18 will beinitialized and the control program contained therein executed,beginning in block 302.

In block 302, the oil replacement controller 18 will reset an intervaltimer variable, an interval mileage variable, and an interval fuelconsumption value which are preferably stored within the centralprocessing unit of the controller 18. As described below, the intervaltimer and interval mileage variables are used to specify an intervalperiod which limits the iterations of steps used to determine thequantity of oil to be injected into the fuel system. Once the intervalperiod is reached, the injection process will then proceed to determinea base quantity of oil to be injected into the engine's fuel systemduring the specified interval period based on the fuel consumptionvalue.

One of the interval timer variable and interval mileage variable areused as an interval selection variable to specify the interval periodwith the selection of which variable is to be used primarily dependentupon the application in which the internal combustion engine is beingused. That is, if the engine is used in an application in which mileageis a primary factor affecting engine wear, such as in an over-the-roadvehicle, then the interval mileage variable will be used to determinethe interval period. Conversely, if the engine is used in an applicationin which time of operation is a primary factor affecting engine wear,such as in a heavy earth moving vehicle, marine application or generatorset, then the interval timer variable will be used to determine theinterval period.

The process next transfers control to decisional block 304, where it isdetermined if the interval selection variable (i.e. either the intervaltimer variable or interval mileage variable depending on the specificengine application) has reached a preset interval. If not, controlpasses to block 306 where the interval timer variable and/or theinterval mileage variable are updated and recorded within the controller18 along with the interval fuel consumption value. Control then againreturns to block 304, thus forming an interval loop. The interval timervariable, interval mileage variable and interval fuel consumption valueare updated based on the change in time, mileage and fuel consumptionsince the last iteration of the interval loop, thus resulting in arecord of the cumulative amount of time and mileage in the currentinterval. In the most preferred embodiment of the present invention,cumulative totals for these variables are stored as well as a runninghistory for each iteration of the interval loop. Also, during each passthrough the interval loop, the current fuel consumption rate or fuelconsumption quantity, as provided by ECM 19, is recorded.

Fundamentally, the interval loop acts to limit the iterations of stepsused to determine the quantity of oil to be injected into the fuelsystem of the internal combustion engine. That is, due to the relativelysmall rate of injection of oil to the fuel system, it is only necessaryto calculate the oil injection quantity on a periodic basis,approximately every minute. Thus, in the most preferred embodiment, theinterval loop is structured so that the preset interval will be reachedby the internal selection variable approximately every minute.

Also, the interval loop functions to determine and record the fuelconsumption rate or fuel consumption amount for the current interval.Each time control passes to block 306, a fuel consumption value isdetermined. The fuel consumption value is preferably the instantaneousfuel consumption rate provided directly by ECM 19, as discussedhereinabove. Alternatively, if the engine is not provided with an ECMthe instantaneous fuel consumption rate may be calculated, and thenrecorded, using engine speed and fuel rail pressure information receivedfrom the engine speed and pressure sensors discussed hereinabove. Duringeach interval, the instantaneous fuel consumption values are averaged toobtain an average fuel consumption rate, or fuel consumption quantity,as applicable, for the interval. It should be understood that a fuelconsumption value corresponding to the amount of fuel burned may beprovided instead of a fuel consumption rate value. Preferably, anaverage fuel consumption rate is continuously calculated as eachinstantaneous fuel consumption rate is determined during the currentinterval.

Once the interval selection variable reaches the preset interval,control passes to block 310. In block 310, the system determines thequantity of oil to be injected into the fuel system during the currentinterval based on the fuel consumption value, i.e. fuel consumptionrate. Importantly, the fuel consumption value is directly related to theoperating severity of the internal combustion engine which determinesthe oil replacement needs of the engine. As indicated in block 310, thisprocess of determining the quantity of oil to be injected during thecurrent interval is discussed in more detail below in connection withthe flowcharts shown in FIGS. 4 and 5. FIG. 4 illustrates the preferredprocess of determining the quantity of oil to be injected based on thecurrent fuel consumption while FIG. 5 illustrates an alternativeembodiment. Once the current amount of oil to be injected is determined,this current amount of oil is added to the total amount of oil to beinjected from previous interval periods, if any, to result in acumulated oil quantity to be injected. That is, the amount of oil to beinjected for a certain number of interval periods is summed to form acumulated oil quantity to be injected. As noted below, once thiscumulated oil quantity exceeds a predetermined threshold, an injectionevent is initiated and the cumulated oil quantity reset.

More specifically, once the amount of oil to be injected is determinedand added to the cumulated oil quantity, control passes to decisionalblock 312, where it is determined if the cumulated oil quantity to beinjected exceeds a unit injection quantity. That is, in the mostpreferred embodiment as discussed above, lube oil injection controldevice 16, shown in FIG. 1, is configured to inject a constant amount ofoil (the unit injection quantity or one injection unit) into the fuelsystem of the internal combustion engine upon each actuation thereof.Thus, only when the cumulated oil quantity exceeds the unit injectionquantity is it necessary to initiate an injection event. Otherwise, byincreasing the cumulated oil quantity by the amount of oil to beinjected in the current interval, injection is deferred until suchfuture intervals when the cumulated oil quantity exceeds the unitinjection quantity.

Thus, referring back to FIG. 3, if the cumulated oil quantity does notexceed the unit injection quantity, control passes to block 314 wherethe cumulated oil quantity is recorded for later use. Control thenpasses to block 316, where the interval timer variable, interval mileagevariable, and interval fuel consumption value, are reset to zero inpreparation for the next interval loop, and finally control returns toblock 304, where the system again enters the interval loop.

If the cumulated oil quantity exceeds the unit injection quantity inblock 312, then control passes to block 318 where an injection event isinitiated. Specifically, in block 318, a solenoid control signal isgenerated by the oil replacement controller 18 and supplied to lube oilinjection control device 16 (shown in FIG. 1) to initiate the injectionof one injection unit of oil, for example, one ounce.

Control then passes to block 320, where the cumulated oil quantity isreset to zero. That is, in view of the injection event occurring inblock 318 as a result of the cumulated oil quantity exceeding the unitinjection quantity, the cumulated oil quantity is reset to zero to allowfor the quantity of oil to be injected in future intervals to besimilarly accumulated. Of course, one of skill in the art willappreciate that the cumulated oil quantity could be reduced only by theunit injection quantity (instead of being reset to zero) to provide forgreater accuracy in the oil replacement system of the present invention,if necessary. Control then passes to block 316, where the interval timervariable, interval mileage variable, and interval fuel consumptionvalue, are reset to zero, and finally control returns to block 304,where the system again enters the predetermined interval loop.

As noted above, the determination of the quantity of oil to be injectedinto the fuel system during any given time interval is determined basedon the fuel consumption of the internal combustion engine. As theoperating conditions of the engine vary, the fuel consumption rate ofthe engine varies resulting in variations in the quantity of oil to beinjected. As the quantity of oil to be injected varies, the timing ofoil injection and thus the injection flow rate varies since the timerequired to produce a unit injection quantity will vary. The processemployed in the most preferred embodiment of the present invention tocalculate the quantity of oil is illustrated in FIG. 4.

As discussed hereinbelow, the most preferred embodiment of the presentinvention uses a fuel consumption value as an indication of the engineoperating severity since fuel consumption closely correlates to theoperating severity of the engine and thus the deterioration of the lubeoil. However, other engine operating parameters which correlate to theseverity of engine operation may be used, such as engine exhaust airtemperature. The engine operating severity value, i.e. preferably anaverage or total, depending on the parameter, as opposed to aninstantaneous value, would be calculated for a current interval ofengine operation and used in the process of the present invention in asimilar manner as the fuel consumption value. Of course, the correlationof the engine operating severity value to the severity of engineoperation and the determination of the oil to be injected would bedependent on the particular severity value used as discussedhereinbelow.

As seen in FIG. 4, the process begins in block 400 where the systemdetermines the internal combustion engine type and configuration basedon initial set-up information provided to the oil replacement controller18. Initial set-up information for a plurality of internal combustionengine types and configurations could be stored, for example, in memory216 discussed above in connection with FIG. 2 and could be selectedbased on a DIP switch or jumper connection on the oil replacementcontroller 18, such as through the use of engine type selection switches232. Alternatively, the internal combustion engine type andconfiguration information could itself be provided by an external DIPswitch, jumper block, or the like.

The configuration information could include, for example, the specificfuel system in use on the internal combustion engine and any othersuitable information impacting the fuel consumption of the engine. Foreach combination of engine type and configuration information, thesystem includes a data table of oil change periods corresponding torespective fuel consumption values of the internal combustion engine.

Control then transfers to block 402, where the fuel consumption value ofthe internal combustion engine is used as an index to the data tablecorresponding to the engine type and configuration information, to thusaccess an oil change period corresponding to the current operationalstate of the internal combustion engine. Thus, for any given fuelconsumption value as determined for the current interval, a current oilchange period for the type and configuration of the engine isdetermined. Control then passes to block 404 where the current oilchange period is divided into the oil capacity of the internalcombustion engine to determine a baseline quantity of oil to be injectedinto the fuel system of the internal combustion engine.

For example, for an engine currently having a fuel consumption value of7 miles-per-gallon, an oil change period of 25,000 miles is determinedfrom the appropriate data table in block 402. If the engine has an oilsump capacity of 11 gallons, then the baseline quantity of oil to beinjected is equal to 11 gallons divided by 25,000 miles, orapproximately 0.06 ounces-per-mile. If, however, the same engine isoperating at a fuel consumption value of 5 miles-per-gallon, the oilchange period is determined in block 402 to be 12,000 miles. Thus, thebaseline quantity of oil to be injected is equal to 11 gallons dividedby 12,000 miles, or approximately 0.12 ounces-per-mile.

As discussed hereinabove, an alternative embodiment may use an engineoperating severity value other than fuel consumption, such as engineexhaust air temperature and lube oil soot contamination levels. In thiscase, the oil change period would be accessed in block 402 using aspecific data table correlating the particular engine operating severityvalue to the oil change period.

Control next transfers to block 406, where the baseline quantity isadjusted by the oil temperature. In the most preferred embodiment, ifthe oil temperature is over 255° F., the baseline quantity will beincreased by as much as 50%, generally in proportional relationship tothe amount by which the oil temperature exceeds 255° F.

In blocks 408 and 410, the system next adjusts the baseline quantitybased on the soot producing characteristics of the internal combustionengine operating at the specific fuel consumption value. Thus, in block408, the system first reads a soot data table to determine the soot rateof the engine for the current interval fuel consumption value and fuelquality. This value is used in block 410 to adjust the baseline quantityof oil to be injected such that a higher soot rate results in anincrease in the baseline quantity of oil to be injected, while a lowersoot rate results in a decrease in the baseline quantity of oil to beinjected.

In accordance with the most preferred embodiment of the presentinvention, the baseline quantity of oil to be injected can optionally befurther adjusted in accordance with a number of factors, if desired.Specifically, in block 412 for example, the baseline quantity can beadjusted based on the quality of the oil used in the internal combustionengine. Thus, if the engine is using a higher quality oil having alonger life span, then the amount of oil to be disposed throughinjection into the fuel could be reduced. Conversely, if a lower gradeoil is used, the amount to be injected could be increased accordingly.Also, although not shown in FIG. 4, adjustments could be made to thebaseline quantity based on the sulfur content of the fuel. Uponcompletion of the process illustrated in FIG. 4, control returns atblock 414 to block 312 shown in FIG. 3.

A second embodiment of the process for calculating the quantity of oilto be injected for a particular interval is illustrated in FIG. 5. Inthis embodiment, the quantity oil to be injected is based on a desiredoil concentration value. The oil concentration value which may varydepending on the engine type and configuration. The process begins inblock 500 where the system determines the internal combustion enginetype and configuration based on initial set-up information provided tothe oil replacement controller 18. As with the previous embodiment ofFIG. 4, initial set-up information for a plurality of internalcombustion engine types and configurations could be stored, for example,in memory 216 discussed above in connection with FIG. 2 and could beselected based on a DIP switch or jumper connection on the oilreplacement controller 18, such as through the use of engine typeselection switches 232. Alternatively, the internal combustion enginetype and configuration information could itself be provided by anexternal DIP switch, jumper block, or the like. The configurationinformation could include, for example, the specific fuel system in useon the internal combustion engine and any other suitable informationimpacting the fuel consumption of the engine.

Control then transfers to block 502, where the specific engine type andconfiguration of the internal combustion engine is used as an index to adata table to access an oil concentration value. Control then passes toblock 504 where the oil concentration value is multiplied by the currentfuel consumption value or rate of the internal combustion engine todetermine a baseline quantity of oil to be injected into the fuel systemof the internal combustion engine. For example, for a given engine typeand configuration, an oil concentration value of 0.03% may be accessedin block 502 and multiplied by the current fuel consumption value of,for example, 7 miles-per-gallon to obtain the current baseline quantityof oil to be injected.

Control next transfers sequentially to blocks 506, 508, 510 and 512where the baseline quantity is adjusted based on the oil temperature,the soot producing rate of the fuel and the quality of the lube oil, asdiscussed with respect to the preferred embodiment of FIG. 4. Uponcompletion of the process illustrated in FIG. 5, control returns atblock 514 to block 312 shown in FIG. 3.

Referring next to FIG. 6, a second important aspect of the presentinvention in which a diagnostic process is performed to monitor the oilsump level, to transfer oil from auxiliary oil tank 40 to primary oilsump 24 if necessary, and to alert an operator to a fault condition inthe oil replacement system of the present invention will now bediscussed in detail. As seen in FIG. 6, the most preferred embodiment ofthe diagnostic process begins at block 600 when an internal combustionengine containing an oil replacement system in accordance with thepresent invention is started. Upon starting of the internal combustionengine, the controller 18 containing the diagnostic process will beinitialized and the control program contained therein executed,beginning in block 602.

In block 602, the diagnostic process first reads the oil sump levelsensor to determine the oil level in primary oil sump 24. Havingdetermined this level, the process transfers control to decisional block604, where the process determines if the primary oil sump level iseither high or low. If the oil level is neither high nor low, controlreturns to block 602 to form an oil sump level monitoring loop.

If it is determined in decisional block 604 that the oil level is high,control transfers to decisional block 606, where it is determined if thesolenoid associated with auxiliary oil flow control device 44 isfunctional. That is, as described above in connection with FIG. 1, thesolenoid of auxiliary oil flow control device 44 can be actuated toallow oil from auxiliary oil tank 40 to be supplied to primary oil sump24. However, should the solenoid of device 44 be defective or stuck inan open condition, it could result in overfilling of the primary oilsump 24. Therefore, in accordance with the most preferred embodiment ofthe diagnostic process shown in FIG. 6, if the primary oil sump level ishigh, the diagnostic process verifies proper operation of the solenoidassociated with control device 44 to ensure that the excess oil inprimary oil sump 24 is not the result of the solenoid of control device44 being defective.

If it is determined that the solenoid of auxiliary oil flow controldevice 44 is not functional, then control transfers to block 608 where afault code is generated to the vehicle operator indicating that thesolenoid/control device 44 may be malfunctioning and that a manualshutdown procedure may be necessary. If it is determined that controldevice 44 is functioning properly, then control returns to block 602 tocontinue monitoring the oil level in primary oil sump 24.

If in decisional block 604 it is determined that the oil level in theprimary oil sump is low, control transfers to block 610, where thediagnostic system generates a signal commanding oil injection from theauxiliary oil tank to primary oil sump 24. That is, as a result of thedetermination that the primary oil sump level is low, the diagnosticsystem adds oil from auxiliary tank 40 to primary sump 24.

Control then transfers to decisional block 612, where the processdetermines if the primary oil sump level is medium. If the oil level ismedium, then the oil addition performed in block 610 was sufficient toreplenish primary oil sump 24 and control transfers to block 606 toverify that the solenoid of auxiliary oil control device 44 isfunctioning properly. If the oil level is not medium, then the oiladdition performed in block 610 was insufficient to replenish theprimary oil sump, and control transfers to decisional block 614.

In decisional block 614, the diagnostic process determines if theauxiliary oil tank level sensor is low. That is, the diagnostic processreads an auxiliary oil tank level sensor and processes the resultinglevel information to determine if sufficient oil remains in auxiliaryoil tank 40. If auxiliary tank 40 does not contain a sufficient amountof oil (i.e. the level is low), then control transfers to block 616where a fault code is generated alerting the operator of the need to addoil to auxiliary oil tank 40. Control then returns to decisional block618 discussed hereinbelow. If it is determined in decisional block 614that the auxiliary oil tank level is not low, the control transfersdirectly to decisional block 618.

In decisional block 618, the diagnostic process determines if thesolenoid of auxiliary flow control device 44 is functional. That is, thediagnostic process makes a similar determination as that made indecisional block 606. In block 618, however, if it is determined thatthe solenoid is functional, then control returns to block 610, whereadditional oil is transferred from auxiliary oil tank 40 to primary oilsump 24. This process continues until the primary oil sump level hasbeen adequately replenished.

If, however, it is determined in decisional block 618 that the solenoidof control device 44 is not functional, then control transfers to block620 where a fault code indicating that oil should be manually added toprimary oil sump 24 is generated to the operator of the vehicle. Controlthen returns to block 610 to continue attempts at transferring oil fromauxiliary oil tank 40 to the primary oil sump 24.

Having described the most preferred embodiment of the diagnostic processof the present invention above in detail, it should be appreciated thatvarious alterations to this system could be made within the scope of theinvention. Specifically, if the primary oil sump level sensor only has a"low" output, then the diagnostic process of FIG. 6 could be simplifiedsuch that as a result of the low level signal, oil is transferred fromauxiliary tank 40 to the primary oil sump 24. Furthermore, it ispossible that the vehicle would not be equipped with auxiliary oil tank40, it which case it would not be possible to replenish oil to primaryoil sump 24. In this case, the diagnostic process would merely generatean appropriate dashboard indicator to the vehicle operator indicatingthe need for oil addition, etc. Finally, the diagnostic process of thepresent invention will also record the amount of oil being transferredfrom auxiliary tank 40 to the primary oil sump 24 and compare this valueat regular intervals with the fuel consumption value and/or the amountof oil injected into the fuel system of the engine. By making thiscomparison, the diagnostic process can determine if the replacement rateis higher or lower than the injection rate to detect an oil pan leak orother malfunctioning.

The present lube oil replacement system results in several importantadvantages. First, the present system maintains the quality of the lubeoil in sump 24 at an optimum level throughout engine operationregardless of engine operating conditions. Fundamentally, the presentsystem is capable of automatically and continuously determining thecurrent level of distress or wear imparted upon the oil based on varyingengine operating conditions and continuously adjusting the replacementrate to obtain an optimum level of engine lubrication throughout engineoperation. This is accomplished by variably controlling the amount ofoil drained from the sump and injected into the fuel system based on theseverity of engine operation as indicated by, for example, fuelconsumption of the engine, and other factors such as engine temperatureand oil soot contamination levels. Generally, when the engine operatesat above normal capacity and increased load, the fuel consumption rateincreases and the rate of oil degradation increases. In response, thepresent system will increase the frequency of used lube oil injectionsinto the fuel system and accordingly increase the frequency of new lubeoil injections from auxiliary tank 40 into sump 24. On the other hand,if the engine begins to operate at a reduced capacity under lighterloads, fuel consumption will decrease resulting in less than normal oildegradation. In response, the present system will decrease the frequencyof used lube oil injections into the fuel system and accordinglydecrease the frequency of new lube oil injections from auxiliary tank 40into sump 24. The present system variable controls the frequency of lubeoil replacement by controlling the frequency of operation of injectioncontrol device 16 and auxiliary lube oil flow control device 44. Incomparison, most conventional "preset" continuous lube oil replacementsystems do not adequately maintain the quality of the lube oil in thesump. A conventional "preset" continuous lube oil replacement systeminjects predetermined quantities of lube oil at preset time intervalsthroughout engine operation. The injection quantity or the frequency ofinjections is adjustably set to cause replacement of the entire sumpaccording to the regular recommended oil change period for theparticular engine regardless of engine operating conditions. If theengine is operated at greater than normal capacity, the conventionalsystem will continue to inject the same quantity of oil over time. As aresult, over time, the lube oil will periodically reach levels of highdegradation causing increased engine wear. This comparative advantage ofthe present invention over conventional "preset" systems is shown byExample I and Table I.

EXAMPLE I

Each engine is an M11 engine, manufactured by the assignee of thepresent invention, Cummins Engine Co., Inc., having a 100 gallon fueltank and an 11 gallon oil sump. The engine pumps 40 gallons per hour offuel through the fuel system continuously. When operating at full power,this engine will burn approximately 16 gallons per hour with theremaining returning to the fuel tank. When operating at nearly no load,the engine will burn 4 gallons of fuel per hour. The fuel is a lowsulfur fuel with 0.045% sulfur and the lubricant contains 0.45% sulfur.

Engine A includes a conventional "preset" injection system with a presetinjection rate of lube oil into the fuel system based on no loadconditions. Engine B includes the present continuous lube oilreplacement system. The engines are operated at full power, i.e. underfull load conditions, for the recommended oil change period of 12,000miles for full power operation. As shown in Table I, the conventionalsystem in engine A fails to respond to the need for increased oilreplacement under the heavier operating conditions of the engine by onlyreplacing 2.7 gallons under full power conditions. As a result, the lubeoil in the engine's lube oil system becomes over-used causing increasedengine wear. The present system, on the other hand, replaces 11.4gallons of oil thus providing optimal engine protection.

                  TABLE I                                                         ______________________________________                                                                     Fuel sulfur                                              Oil replaced in                                                                        Oil         content                                                  12,000 miles                                                                           concentration                                                                             including used                                           (gallons)                                                                              in fuel (%) oil (%)                                          ______________________________________                                        Engine A -                                                                              2.70       0.2         0.045                                        Conventional                                                                  "preset"                                                                      system                                                                        Engine B- 11.4       0.8         0.047                                        Present system                                                                ______________________________________                                    

Also, by frequently adjusting the rate of oil replacement to inject onlythe required amount of oil according to engine fuel consumption, thepresent system avoids wasting oil. Conventional "preset" lube oilreplacement systems, which are preset to inject oil at a ratecorresponding to normal or high engine operating capacity, will continueto inject more oil than necessary resulting in unnecessary costs to theoperator. Example II and Table II set forth this comparative advantageof the present invention over conventional "preset" systems.

EXAMPLE II

The type of engine, fuel and lubricant is the same as described inExample I hereinabove. Also, engine A includes a conventional "preset"injection system while engine B includes the present continuous lube oilreplacement system. However, engine A is now preset with a lube oilinjection rate based on full engine power operation and the engines areoperated at no load. Since the oil change recommendation at full poweris 11 gallons every 12,000 miles, the oil change recommendation at noload will be significantly less the 11 gallons every 12,000 miles.However, as shown in Table II, the amount of oil replaced in engine A at12,000 miles even exceeds the full power recommendation. Thus, it isshown that the conventional "preset" system unnecessarily injects, andtherefore wastes, approximately 14 gallons of oil. The present system,on the other hand, automatically compensates for the decreased load byinjecting less oil into the fuel system.

                  TABLE II                                                        ______________________________________                                                                     Fuel sulfur                                              Oil replaced in                                                                        Oil         content                                                  12,000 miles                                                                           concentration                                                                             including used                                           (gallons)                                                                              in fuel (%) oil (%)                                          ______________________________________                                        Engine A- 20.3       1.70        0.052                                        Conventional                                                                  "preset"                                                                      system                                                                        Engine B- 6.24       0.56        0.047                                        Present system                                                                ______________________________________                                    

Another advantage of the present invention is the ability to maintainthe lube oil concentration in the fuel below a level necessary tomaintain the sulfur content of the fuel below the acceptable limit of0.05%. It has been found that, for the typical oil, the lube oilconcentration in the fuel should be less than 1% at all times duringengine operation and preferably approximately 0.5% to maintain thesulfur content of a typical low sulfur fuel below 0.05%. Conventionalsystems are less capable of maintaining the sulfur content below 0.05%since at certain engine operating conditions more oil will be injectedinto the fuel system than is necessary. The likelihood of conventionalsystems resulting in unacceptably high sulfur levels in the fuel isespecially high when the engine is operating at a capacity less than thecapacity corresponding to the preset injection rate. As shown in ExampleII and Table II, the conventional "preset" system may inject anexcessive amount of lube oil into the fuel causing the cumulative sulfurcontent of the oil and fuel to exceed the acceptable limit of 0.05%.Excessive oil concentrations may also adversely affect the engineemissions resulting in emissions noncompliance. The present systemmaintains the sulfur concentration within acceptable limits by varyingthe injection rate based on engine conditions and is also more likely tomaintain emissions within regulatory limits throughout operation of theengine. As shown in Table I, although the present system injects moreoil to provide optimal engine protection at higher engine loads, thefuel sulfur content and oil concentration are maintained withinacceptable limits.

Industrial Applicability

The present continuous lube oil replacement system may be used in anyinternal combustion engine having a supply of lubricating fluid forlubricating the engine's components. However, the present system isparticularly useful in a compression ignition engine of any vehicle,such as a truck or boat, or industrial equipment, such as constructionor earth moving machines.

We claim:
 1. A method for electronically controlling lube oilreplacement in an engine having a lube oil system and a fuel supplysystem for supplying fuel to the engine, comprising:intermittentlyinjecting injection quantities of used lube oil into the fuel supplysystem from the lube oil system; detecting at least one engine operatingcondition; generating an engine operating condition signal indicative ofsaid at least one engine operating condition; calculating an engineoperating severity value based on said engine condition signal;generating an injection flow control signal based on said engineoperating severity value; and controlling the operation of said lube oilinjection control means based on said injection flow control signal tovary a frequency of intermittent injection of said injection quantitiesof used lube oil.
 2. The method of claim 1, wherein said engineoperating severity value is a fuel consumption value corresponding to afuel consumption of the engine during an operating interval.
 3. Themethod of claim 1, further including the step of adjusting the frequencyof intermittent injection of said injection quantities based on aquality characteristic of the lube oil.
 4. The method of claim 1,further including the steps of providing an auxiliary supply flow oflube oil to the engine and controlling said auxiliary supply flow oflube oil to said engine.
 5. The method of claim 4, further including thestep of generating an auxiliary flow control signal for controlling theflow of said auxiliary supply flow of lube oil.